Cheese method
Press F12 to open the console and enter:
var r = cr_getC2Runtime();
Start each level and run the following code to instantly win it, replacing X with the number of pieces, shown at the bottom of the level select. After doing this for all 20 levels you should have all achievements. (You can press the up arrow key with the console text input field focused to copy the previous command.)
It's possible there is a faster method. You can unlock all levels at once with the console but it doesn't grant achievements.
Original curation by NEXGENEEZY. Console method provided by Bobogoobo. Thanks to DDtective for finding the console.
